1. Field of the Invention
The present invention relates to the field of semiconductors and, more particularly, to tools for validating power requirements associated with microprocessors.
2. Prior Art
An overwhelming demand is being placed on power systems of current and future generations of personal computers (PCs), as well as on other computing devices utilizing microprocessors. Newer and higher performance processors generally require more power, yet operate at reduced voltage levels. Additional power requirements are due to a number of reasons, but primarily due to the sheer number and density of transistors being packaged on a chip, coupled with the requirement of operating at a much faster clock frequency. Thus, enhancements in computing speed and capability of a microprocessor place considerable constraint on a power supply (or system) providing the necessary power for operating the processor.
With the advent and proliferation of laptop, notebook, sub-notebook, pocket and hand-held computers, a trend has been to include power management functions for use on microprocessors and peripherals in the PC. Power management is required to extend the battery life of portable computers. Reduced power consumption also aids in reducing heat dissipation, as well as lowering the energy costs associated with the operation of a PC. These energy cost reduction constraints will be more pronounced in the future as the computer industry attempts to become "environmentally friendly" or more "green."
Although power management functions have their benefits, these requirements place severe constraints on the power supply. A PC "waking" from its "dormant" (or "sleep") state to its fully operational state can transition from a few milliamperes to several amperes in a very short span of time. For example, one power managed microprocessor has a minimum current draw of approximately 1 mA and a maximum current draw of approximately 1.2 A. An almost instantaneous change from minimum to full maximum current results in a significantly high current transition, which is referenced as di/dt. In the example above, a change of 1 mA to 1.2 A in a matter of 100 nanoseconds results in a di/dt of approximately 1.2.times.10.sup.7 A/sec. ((1.2 A-1 mA) .div.100.sup.-9 sec.), which is quite significant. The di/dt problem is exacerbated when processors are made to operate at lower supply voltages, since the current drawn is increased in order to provide the same amount of power to the processor. This increase in current will then result in a higher di/dt.
It is evident from the above description that future microprocessors and PCs will require power supplies that can cope with these constraints. A typical low cost switching power supply, such as is found in current state-of-the-art PCs, is not designed for low minimum loads nor can it maintain regulation when the load changes rapidly over a significant range, such as when a processor undergoes a power management transition. The power supply can have a poor level of transient response that can lead to apparently random failures of the processor. While this failure may not permanently damage the processor, it can result in lost data. Diagnosing repeated failures may be extremely difficult, since such problems will more than likely be dependent on the software executing the power routine. In some instances, poor transient response can cause the supply voltage to rise to dangerous levels and may in fact damage components, including the microprocessor. In any event, failures due to poor response by the power supply are not acceptable from a reliability perspective.
In order to ensure that adequate power supply capabilities exist for a system, it is preferable to test a given power supply under operating conditions. Therefore, an OEM (original equipment manufacturer) can manufacture a system (component or an assembly), which includes a microprocessor, and test for the desired power requirements. Adequate power supplies can then be selected or designed in conjunction with "cycling" the processor through its various power transitions. However, this assumes that a fully functional microprocessor is available for such tests.
An alternative approach is to simulate the power requirements of a microprocessor by utilizing some form of hardware or software emulation. However, such emulation will necessarily take some amount of engineering on the part of the OEM to emulate the power requirements of the microprocessor. The present invention, on the other hand, is a power validation tool (or device) that is designed to be a physical substitute for the microprocessor from a power perspective, in order to determine the response characteristics of the power supply.